WASHINGTON — A nonpartisan, independent review of interrogation and detention programs in the years after the Sept. 11, 2001, terrorist attacks concludes that “it is indisputable that the United States engaged in the practice of torture” and that the nation’s highest officials bore ultimate responsibility for it.

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The use of torture, the report concludes, has “no justification” and “damaged the standing of our nation, reduced our capacity to convey moral censure when necessary and potentially increased the danger to U.S. military personnel taken captive.” The task force found “no firm or persuasive evidence” that these interrogation methods produced valuable information that could not have been obtained by other means. While “a person subjected to torture might well divulge useful information,” much of the information obtained by force was not reliable, the report says.

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But the report’s main significance may be its attempt to assess what the United States government did in the years after 2001 and how it should be judged. The C.I.A. not only waterboarded prisoners, but slammed them into walls, chained them in uncomfortable positions for hours, stripped them of clothing and kept them awake for days on end.